The invention relates to an apparatus comprising an electrical device having a first connection terminal and a second connection terminal and further comprising a holder for holding a voltage source having a first voltage-source terminal and a second voltage-source terminal, which holder has a first contact, a second contact and a third contact for cooperation with the voltage-source terminals, via which contacts the first connection terminal is connectable to the first voltage-source terminal and the second connection terminal is connectable to the second voltage-source terminal.
Such an apparatus is known as a hearing aid from DE-U 90 10 347. The known apparatus comprises a battery holder adapted to hold a battery, particularly a button-type battery. The holder has three contact springs, i.e. one central contact spring and two end contact springs disposed adjacent the latter. The central contact spring is electrically connected to electrical components of the hearing aid, such as a microphone, an amplifier, a loudspeaker and the like. Both end contact springs are electrically interconnected and are jointly electrically connected to said electrical components. The battery holder has a special positioning construction in the battery compartment in order to ensure that after it has been placed into the battery compartment a button-type battery is exclusively in contact with the central contact spring and one of the end contact springs, the central contact spring being in contact with one battery terminal and the relevant end contact spring with the other battery terminal.
Although the known apparatus provides a solution in order to prevent a battery from being placed the wrong way around into a battery holder of a hearing aid, the known apparatus has some drawbacks. One of the drawbacks is that the adopted solution imposes stringent mechanical requirements on the holder, particularly as regards the permissible tolerances of the positioning construction which is used. The precision of this construction should be very high in order to guarantee reliable contact-making even after frequent battery replacement. Another drawback is that the interconnected end contact springs may simultaneously come into contact with the battery terminals during or after placement of the battery and thus cause a short-circuit.